Interval timer
Work, rest, work, rest. Both durations are imposed, and it is their ratio that decides what the session actually trains.
OPEN A 30 / 15 × 8The timer opens already set up. Nothing to configure, nothing to install.
What is interval training?
Interval training alternates phases of work and phases of rest, both of a fixed duration. It is the oldest and most general format: it assumes no particular exercise, only a rhythm. Running, cycling, rowing, bodyweight, heavy bag — the timer does not change.
It is also called HIIT when the work phases are taken to very high intensity, close to maximum. All HIIT is interval training; the reverse is not true, since intervals can perfectly well be run at moderate intensity.
The ratio, the only decision that matters
The relationship between work and rest determines which energy system you load. It is the setting that changes everything, far more than the choice of exercise.
| Ratio | Example | What it trains |
|---|---|---|
| 1:3 | 15 s / 45 s | Power — the long rest lets you repeat a maximal effort |
| 1:1 | 30 s / 30 s | General work, the safest starting point |
| 2:1 | 40 s / 20 s | Anaerobic capacity, the most uncomfortable zone |
| 3:1 | 3 min / 1 min | Endurance, threshold |
A frequent mistake: reaching straight for 2:1 because it "looks serious". A 30/30 held cleanly over twelve rounds beats a 40/20 that falls apart at the fifth.
Three worked sessions
The 30 / 15, eight rounds
Six minutes in all, warm-up aside. The most versatile format: short enough to hold the intensity, long enough to count. Open.
The 40 / 20, ten rounds
Ten minutes, markedly harder. Save it for a movement you own: technique degrades fast when the rest is short. Open.
The 3 min / 1 min, five rounds
Twenty minutes, endurance-oriented. Running or rowing rather than bodyweight. Open.
Why a dedicated timer
An ordinary stopwatch leaves you counting the intervals in your head. That holds for three rounds. From the sixth, out of breath, the rest quietly stretches — and the ratio you chose so carefully no longer exists.
Round & Rest changes the colour of the whole screen at each phase: red on work, blue on rest. The transition registers in peripheral vision, without reading the clock, phone flat on the floor. Two sound cues only — one at the start of each effort, one at the end of the session.
Chaining several exercises
When a session has several movements of different durations, plain intervals are no longer enough. The Circuit mode allows several blocks, each repeating its own list of exercises, with rest between rounds and more rest between blocks. Set it up in the app.
OPEN A 40 / 20 × 10Or set work, rest and rounds however you like.